Borates useful for the prevention/mitigation of microbiologically influenced corrosion and staining

ABSTRACT

The present invention discloses methods for 1) preventing and/or mitigating microbiologically influenced corrosion (MIC) and 2) controlling and/or reducing the growth of at least one anaerobic, facultative anaerobic, or microaerophilic microorganism, which includes the step of adding or applying a composition containing a borate salt to an area susceptible to MIC and/or growth of anaerobic, facultative anaerobic, or microaerophilic microorganisms, in an effective amount to 1) control and/or reduce the growth or 2) to prevent and/or mitigate the corrosion. The present invention also discloses various means of using the compositions of the present invention which contain borate salts and further sets forth methods for preventing and/or mitigating staining caused, at least in part, by at least one anaerobic, facultative anaerobic, or microaerophilic microorganism.

This is a divisional of application Ser. No. 08/231,715 filed Apr. 22,1994 now U.S. Pat. No. 5,654,012

BACKGROUND OF THE INVENTION

The present invention relates to certain compositions and methods usefulfor preventing and/or mitigating microbiologically influenced corrosionand staining occurring, for example, in a sealed environment.

Microbiologically influenced corrosion (MIC) of the internal surfaces ofequipment such as pipes, tanks, and heat transfer components, inaddition to non-MIC electrochemically influenced corrosion, results inextensive "remove and replace" maintenance projects. This is usuallyvery costly and time consuming.

An alternative procedure used in some situations is to install an insertor lining, in situ, composed of a resin (e.g., epoxy or vinyl esters)system that forms a barrier between the host component, e.g.transmission pipe line, and the fluid being transported through the pipeline. Once in place, this lining provides a means of mitigating theeffect of the corrosion. However, it may not prevent the corrosionmechanism from continuing to degrade the host component.

Wide-spread forms of MIC occur where anaerobic conditions exist. MIC isoften identified as including pitting corrosion or "under-deposit"corrosion.

Microorganisms involved include sulfate reducing bacteria (SRB) andClostridium types which produce H₂ S or H₂ that attack the metal. Themicroorganisms' source of inoculum is virtually unlimited. However, thecorrosion caused by their growth occurs only when specific conditionsexist such as an oxygen free environment. The microorganisms can grow tovery large populations in localized sites and attack the host component,e.g., metal, causing a very aggressive corrosion condition.

Furthermore, inserting a lining or barrier on the inner surface of apipe line may provide the ideal anaerobic environment for microorganismsto grow and subsequently influence corrosion of the host component.Cleaning and removing the debris and corrosion by-products, found oninner surfaces where the lining would interface, is a necessary step toinsure proper application. However, this cleaning typically will noteliminate the microorganism inoculum source. Even under the best caseconditions where cleaning was exceptionally complete, and theinstallation of the lining was flawless, the potential for MIC to beinitiated or to resume activity is very high.

A four year study made under actual plant operating conditions examinedvarious corrosion mechanisms involved with typical service water systemmaterials of construction. Corrosion coupons were included as part ofthe test samples. Some of the coupons were placed in a position wherethe insert liner was placed as a barrier to provide the host componentprotection from corrosion. A few of the liner samples were intentionallyflawed to simulate installation problems. Unlike actual plantinstallation of the liner, however, the base materials were coated withan epoxy adhesive to insure the liner material was attached to thecoupon. It was known that the epoxy adhesive was not a specific moisturebarrier; however, it should have provided some additional protectionagainst corrosion of the base material. Some observations made duringthe study that related to MIC included:

1. Coupons in stagnant, intermittent, and continuous flow positions weresusceptible to MIC.

2. The lack of tuberculation formation does not imply MIC has notoccurred.

3. If there is damage to the coating or lining and the felt is notimpregnated with resin, water will wick through and promote corrosion ofthe base metal.

4. Due to the specific water chemistry of the test site, no significantcorrosion under the liner occurred, but other sites with differentchemistries could experience severe corrosion.

Another type of liner that creates an anaerobic environment is the linerused in swimming pools. These types of liners are affected by stainingcaused, in part, by facultative anaerobic, anaerobic, or microaerophilicmicroorganisms.

The staining can be described as intense black-brown or gray isolatedspots, or more diffuse gray discoloration of the vinyl surface andblotchy in appearance. The discolorations are, for example, locatedbelow the water level usually on the sloping sides and on the bottom ofthe pools. Staining has been observed at depth of 2-3 feet and to 9feet. In most cases, the staining was localized where the back-sidesurface of the liner came into direct contact with the cement/sand orcement/vermiculite base used to form the pool in-ground and upon whichthe vinyl liner was placed. Rarely was staining observed on water-sidesurfaces where the back-side surfaces were in direct contact withgalvanized metal vertical walls, or poured concrete/concrete blockvertical walls. Stereoscopic microscope examination of the water-sidestained surfaces of the liner indicated that the stain was notspecifically the result of substances adhering to or adsorbed onto thevinyl surface which was exposed to the pool water. In fact, theseobservations indicated that the stain appeared to originate on theback-side surface and diffuse through the vinyl, appearing as adisfigurement on the water-side surface.

Staining occurred in pools routinely treated with oxidizing biocidessuch as hypochlorite salts, tri/dichloroisocyanurate, and brominecompounds to control growth of algae and other microorganisms. It alsooccurred in pools treated with nonoxidizing algicides such as quaternaryammonium salts and polyquat compounds often used in conjunction withoxidizing biocides. These investigations indicated that the chemicalcharacteristics of the pool water (such as pH, hardness, and alkalinity)had no correlation to the occurrence of the staining. Staining wasobserved most frequently on liners that had been in place for 5-15years. The stains usually appeared gradually over that time. However, itwas also reported that liners used to replace the stained liners becamestained in the same general location within a period as short as oneyear after replacement.

In addition to promoting an anaerobic environment, the inherent physicalcharacteristics of liners and the procedures used to install themprovide many ideal opportunities for the growth of anaerobic,facultative anaerobic, or microaerophilic microorganisms which can leadto staining or MIC.

The need to prevent MIC or staining or to mitigate an existing MIC orstaining situation is clear. The key to preventing or mitigating MIC orstaining is to prevent the growth of the microorganisms responsible forthe MIC or staining. This can be done by including into the susceptibleenvironment a biocide-biostat with efficacy in controlling or reducingthe growth of facultative anaerobic, anaerobic, or microaerophilicmicroorganisms. The chemical characteristics of the biocide-biostatshould preferably have the following properties: long persistency,minimum water solubility, passive to composition materials of the liningsystem and the host component (e.g., metal), non-hazardous, andenvironmentally acceptable.

Accordingly, a goal of the present invention is to provide compositionscapable of preventing and/or mitigating microbiologically influencedcorrosion, over prolonged periods of time. An additional goal of thepresent invention is to provide a method for biostatically reducing thegrowth of anaerobic, facultative anaerobic, or microaerophilicmicroorganisms. Another goal of the present invention is to provide amethod for preventing and/or mitigating microbiologically influencedcorrosion. A further goal of the present invention is to provide amethod for preventing and/or mitigating the type of staining describedabove.

Additional advantages of the present invention will be set forth in partin the description which follows, and in part will be apparent from thedescription, or may be learned by practice of the present invention. Thegoals and advantages of the present invention will be realized andattained by means of the elements and combinations particularly pointedout in the appended claims.

To achieve the above noted goals and in accordance with the purpose ofthe present invention, as embodied and broadly described herein, thepresent invention provides biocide-biostat compositions useful in 1)controlling and/or reducing the growth of an anaerobic, facultativeanaerobic, or microaerophilic microorganisms and 2) preventing and/ormitigating microbiologically influenced corrosion or staining. Thecompositions contain a borate salt, preferably calcium metaborate,barium metaborate, calcium pyroborate, or mixtures thereof.

The present invention also provides a method for preventing and/ormitigating microbiologically influenced corrosion, for instance, in asealed environment, which comprises the step of adding or applying acomposition of the present invention to an area susceptible to MIC,e.g., inside a pipe to prevent and/or mitigate corrosion.

In addition, the present invention provides a method for controllingand/or reducing the growth of an anaerobic, facultative anaerobic, ormicroaerophilic microorganism which comprises the step of adding orapplying a composition of the present invention to an area susceptibleto the growth of the microorganism. Further, the present inventionprovides a method to prevent and/or mitigate staining caused by amicroorganism comprising the step of adding or applying a composition ofthe present invention to an area susceptible to staining to preventand/or mitigate such staining.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary only and are notrestrictive of the present invention, as claimed.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

With regard to the borate salts useful for the prevention/mitigation ofmicrobiologically influenced corrosion or staining and also useful incontrolling/reducing the growth of an anaerobic, facultative anaerobic,or microaerophilic microorganism, these borate salts should preferablyhave certain chemical characteristics including long persistency (e.g.,remain in biologically active form for at least two years), a minimumwater solubility (e.g., solubility in water in the range of about 0.1 toabout 0.5 percent in water at 21° C.), be passive to compositionmaterials of the lining system and the host component (e.g., metal), benon-hazardous, and environmentally acceptable. Metaborates, andpreferably barium metaborate and calcium metaborate, meet these chemicalcharacteristics and can be used, separately or as a mixture, forpurposes of the present invention. One such commercially availablebarium metaborate is Busan 11-M1, available from Buckman Laboratories,Memphis, Tenn., which is a modified barium metaborate monohydrate. Thetypical properties of this metaborate which are preferred for purposesof the present invention are set forth in Buckman Technical Bulletinsidentified as "Busan 11 M1--A Multifunctional Pigment for the CoatingsIndustry" (Sep. 19, 1983), "Busan® 11 M1--Fire Resistance in Plastics,Paints, Textiles, Rubber, and Adhesives" (1992), and "FormulatingWater-Based Coatings with Barium Metaborate Pigments" (1993), allincorporated in their entireties herein by reference. Other examples ofborate salts include pyroborates and tetraborates such as calciumpyroborate. Besides the calcium and barium boron type salts describedabove, boron salts such as Na, Ammonium, Pb, Li, Mg, K, Sr, or Znborates and boric acid can be used. U.S. Pat. No. 5,066,334,incorporated in its entirety herein by reference, sets forth severalmethods of making metaborates and pyroborates such as calciummetaborate. The borate salts set forth in the '334 patent can be usedfor purposes of the present invention. The solubility of the metaboratesmake them ideal for emulsions. These emulsions can be used in sprayapplications.

As these terms are used herein, "preventing and/or mitigating"microbiologically influenced corrosion, is to be understood that thepresent invention in effect "controls and/or reduces" the growth of atleast one anaerobic, facultative anaerobic, or microaerophilicmicroorganism, responsible, at least in part, for the microbiologicallyinfluenced corrosion or staining. It is to be further understood that by"controlling" (i.e., preventing) the growth of at least one of thesetypes of microorganisms, the growth of the microorganism is inhibited.In other words, there is no growth or essentially no growth of at leastone anaerobic, facultative anaerobic, or microaerophilic microorganism.Thus, the substrates or materials susceptible to attack by these typesof microorganisms are preserved from this attack and the resultingcorrosion or staining caused by the microorganisms. Further, it is to beunderstood that by "reducing" the growth of at least one anaerobic,facultative anaerobic, or microaerophilic microorganism, the level ofmicroorganisms present are biostatically reduced and/or maintained to alow level such that the microbiologically influenced corrosion orstaining is mitigated, i.e., the corrosion or staining rate is sloweddown or eliminated.

The microorganisms controlled and/or reduced by the present inventioninclude anaerobic, facultative anaerobic, and microaerophilic fungi andbacteria. The terms anaerobic (i.e., anaerobe), facultative anaerobic(i.e., facultative anaerobe), and microaerophilic (i.e., microaerophile)as used herein are defined in Bergey's Manual of DeterminativeBacteriology (Ninth Ed.) and these definitions are incorporated hereinby reference. Examples of such microorganisms include, but are notlimited to, sulfate reducing bacteria, Clostridium types which provideH₂ S or H₂ that attack a metal substrate, and Aureobasidium sp. thatcauses staining. Other examples include anaerobic, facultativeanaerobic, and/or microaerophilic microorganisms included in thefollowing genera: Pseudomonas, Arthrobacter Enterobacter, Xanthomonas,and Saccharomvces.

With regard to using borate salts of the present invention in preventingand/or mitigating MIC in an area susceptible to MIC, for instance in asealed environment, e.g., pipe line system, the following preliminaryprocedure should preferably be followed.

In minimizing the impact of MIC in any type of system, whether it is tobe lined or not, it is important to understand the mechanisms of MIC andwhat preliminary mitigation procedures should be considered. One of thefirst considerations for MIC mitigation in systems where a liner insertwill be used, should be the pre-installation cleaning process. The hostcomponent, e.g., pipe, must be cleaned before installing the liner.Several cleaning techniques can be used and each has certain specificcharacteristics. The chemical composition of the materials to be removedby the cleaning is an important consideration, as is the material ofconstruction of the component to be cleaned. Before selecting andimplementing a cleaning procedure, it is suggested that laboratory testdata on deposit analysis and corrosion data be conducted and reviewed.It would be prudent to refer to resource literature on recommendedcleaning practices for industrial process water systems.

While it may not be necessary to return the host component to a "likenew" condition before installing the liner, all debris, existingcorrosion nodules, and macrofouling agents (such as mussels, barnacles,oysters, etc.) should be removed. This removal step not only removes asmany of the MIC causing agents as possible, but also minimizesmechanical or physical damage such contaminants can cause to the liner.

However, even if cleaning is completed, endospore forming microorganismscan persist and still be present in an active or spore state. Under thebest case conditions, assuming a properly cleaned pipe and a flawlessliner installation, the potential for inter-annulus corrosion as aresult of MIC still exists. Anaerobic, facultative anaerobic, andmicroaerophilic bacteria which include pit forming of sulfate reducingbacteria and Clostridium could find the conditions created by theinstallation of the liner appropriate for their survival and growth.

Even after installation, there can be voids between the liner and thehost component. The exact cause of the void is dependent on manyfactors, one of which is the selection of resin chemistry. The epoxyresins are less vulnerable to shrinkage than the vinyl esters.Regardless of the resin used it is likely that there will not be acontinuous bond between the liner and the host pipe. When a void exists,bulk water carrying bacterial inoculum could find its way into theinter-annulus area.

One point of inoculation would be where there is a flaw such as a tearin the felt or a hole in the elastomeric-coating on the internaldiameter of the liner. This can cause wicking or seepage of raw water tothe inter-annulus area. These flaws or entry points may exist to theextent that they allow continuous seepage of bulk water behind the linerand therefore provide repeated inoculation of MIC causing bacteria.

Less than 100% water tight seal is often found at flanges, laterallines, and instrument penetrations. These leaks would also permit thecontinued exposure of the host component, e.g., pipe, to moisture and acontinued inoculum. The potential for other corrosion mechanisms tobecome involved results from the leaks as well.

Thus, the benefits of the present invention include being able to usethe lining to mitigate an existing corrosion condition withoutincreasing the potential for MIC. This application will also preventMIC, compensating for the inherent limitations of installing a flawlesslining. The borate salts have been shown to provide a degree of non-MICcorrosion inhibition as well. In particular, the borate salts provide asufficient source of alkalinity which neutralizes corrosion caused byacid or a low pH. In effect, the borate salts of the present inventionact as pH buffers, which significantly lessen the rate of corrosioncaused by acid or a low pH.

One way to apply the composition of the present invention is in the formof an emulsion of the borate salt which can be made in a liquid vehicleformulation that suspends the borate salt pigment in a flowable form.Suspending agents such as hydroxymethyl cellulose can be formulated withthe borate salt. Preferred emulsions are set forth in the Example whichfollows. This fluid can then, for instance, be sprayed onto the surfaceareas susceptible to MIC, growth of anaerobic, facultative anaerobic, ormicroaerophilic microorganisms and/or staining, which are preferablycleaned. In other words, and referring to a specific use, the fluid issprayed on the component to be treated (e.g., pipe, in-ground poolsubstrate base) to which the lining is applied. The spray applicationcan be achieved in a number of ways and are known by those skilled inthe art. Pipe line applications can also be done by the use of roboticsprayers following cleaning prior to the installation of the lining.Tanks and other similar components can then be spray painted followingcleaning.

The compositions of the present invention can also be used to preventthe initial occurrence of staining on such surfaces as vinyl pool linersurfaces caused, at least in part, by the growth of anaerobic,facultative anaerobic, or microaerophilic microorganisms on the basesubstrate over which the liner is placed. While the specific linerdiscussed herein is a pool liner, other substrates susceptible tosimilar attack by anaerobic, facultative anaerobic, or microaerophilicmicroorganisms are encompassed by the present invention. Thecompositions of the present invention can be dry-blended into thesand/cement or vermiculite/cement substrate used as the base ofin-ground pools. Under preferred circumstances, this should be done whenthe pool liner is initially installed. The compositions of the presentinvention should preferably be added to the base substrate at a level ofabout one pound of borate salt (as commercially received) per about 45pounds of cement mixed with about 145 pounds of sand (or about 20 poundsof vermiculite).

The compositions of the present invention can also be used to preventthe initial occurrence or reoccurrence of staining on liner surfaces(e.g., vinyl pool liners) caused, at least in part, by the growth ofanaerobic, facultative anaerobic, or microaerophilic microorganisms onthe base substrate over which the liner is placed. The borate salt ofthe present invention should be applied to the surface of the basesubstrate during construction of the pool or during the installation ofa replacement liner. Application can be made by spraying or brushapplying a water-based latex formulation containing approximately 18%solids by we ght of the borate salt. This formulation should preferablybe applied at a coverage rate of one gallon per 100 square feet of basesubstrate surface, providing approximately 1.8 pounds of borate salt per100 square foot of substrate surface. Generally, about 1.5 pounds toabout 3.6 pounds of borate salt per 100 square feet of substrate surfacecan be used.

The present invention will be further clarified by the followingexamples, which are intended to be purely exemplary of the presentinvention.

EXAMPLE

From an in-ground swimming pool in Memphis, Tenn. samples of stainedvinyl were obtained and examined using microscopic and microbiologicalisolating culturing techniques known to those skilled in the art.Samples of the sand/cement base substrate where the stained vinyl was incontact were also examined using similar techniques. Several differenttypes of microorganisms were observed growing on the back-side of thevinyl liner. Many of the same microorganisms were found in thesubstrate, and appeared to be growing in the first few inches in depthfrom the interface of the substrate and the vinyl. Samples of thesand-cement substrate, collected from areas where no staining existed,were also examined. Scattered hyphae, but no dense mycelia, wereobserved. Back-side surfaces of the vinyl, where no staining existed,were also examined. Although these surfaces were not sterile, no hyphaeor fungal mycelial masses were observed.

The dominate microflora associated with staining were "Fungi Imperfecti"(molds). No sporulation was observed "in-vivo." However, when isolatesof mycelia, collected from the samples, were cultured on mycophil agar,sporulation occurred. Sporulation also occurred from mycelia on samplesof vinyl when incubated at 37° C. in mold free humidity chambers.

Based on the "in-vitro" sporulation, the dominant microaerophilic,facultative anaerobic and anaerobic fungi were characterized as generain the Moniliacese, e.g. Aureobasidium sp., Torula sp., Phialomyces sp.Aureobasidium sp. and Phialomyces sp. seemed to overgrow the microflorain-vitro. Some bacteria were present in the microflora isolated from thesamples but did not appear to be a significant factor in the occurrenceof the problem.

Efforts to extract and characterize chemically the substancecontributing to the discoloration were not successful. Both organic andaqueous solvents were used to try to remove the discoloration from thevinyl without success. Strong oxidizing solutions, i.e., 5 percentNaOCl, bleached the stain out, but it also bleached out the coloring ofthe vinyl. Infrared analysis comparisons of extracts from both stainedvinyl and non-stained vinyl showed no differences.

Attempts were made to reproduce the staining on pool liner vinylspecimens under laboratory conditions. A sand/cement substrate wasprepared and inoculated with isolates of Aureobasidium sp. Samples ofvinyl were placed in direct contact with the inoculated substrate andincubated at 32° C.± in a humid environmental chamber for 90 days.Extensive growth of fungus occurred both on the substrate and over thesurface of the vinyl in contact with the substrate.

However, no disfiguration of the vinyl occurred under the conditions ofthe test.

From the results and observations made, it was theorized that thestaining was in some way related to the growth of typically occurringsoil-born fungi such as Aureobasidium sp. and Phialomyces sp. on thesubstrate under microaerophilic conditions in contact with the back-sidesurfaces of the vinyl. It was further theorized that as a result of thegrowth of the fungi, a substance, not fungal tissue, was produced"in-vivo" by the mycelial mat that diffused into the vinyl and appearedas a stain or disfigurement on the water-side surface of the vinylliner.

"In-Vivo" Studies

An in-ground vinyl liner pool, located in Memphis, Tenn. where astaining problem had previously occurred, was selected for in-vivostudies. This stained pool liner was originally installed on asand/cement base 13 years prior to liner replacement. Staining appearedon the "floor" of the shallow end (3 foot depth) and on the slopingsides of the deep end (5-7 foot depth) during a period of three yearsprior to replacement. Although staining may have occurred earlier, itwas not readily observed. During the three years prior to linerreplacement, chemicals (e.g. phosphonates and acrylate compounds) wereadded to the pool water to remove or prevent the staining. Thattreatment was not successful.

When the original liner was removed, observations and examinationsdescribed above were made. Prior to installing the replacement liner,two areas three feet by three feet in the shallow end where staining ofthe original liner had occurred were selected as test sites. Theoriginal sand/cement substrate on one site was moved to a depth of threeinches. This was replaced with a substrate composed of:

140 pounds--washed masonry sand;

45 pounds--type A portland cement; and

1 pound=BUSAN 11-M1® modified barium metaborate monohydrate.

The mixture was dry blended, moistened slightly, and troweled into thefloor of the pool. No treatment other than troweling the surface wasdone to the second test site. Following this, the replacement liner wasinstalled in a routine manner.

Visual observations of the two test sites have been made periodicallyduring four swimming seasons subsequent to the liner replacement (i.e. a36 month period). No obvious staining has occurred at either of the twotest sites. However, there appeared to be very slight indications thatstaining may be reappearing at the "deep end" location where staininghad also occurred on the original liner.

"In Vitro" Studies

Laboratory studies were done to determine the efficacy of BUSAN 11-M1®modified barium metaborate monohydrate in preventing the growth of fungion a sand/cement or sand/vermiculite substrate. The following tests weredone:

New Pool Liner Procedures: Dry Blend

Based on the above results, it was assumed that inclusion of BUSAN11-M1® modified barium metaborate monohydrate into the base substratemixture will inhibit the growth of fungi that cause staining. Thisassumption was tested by dry blending BUSAN 11-M1® modified bariummetaborate monohydrate into a sand/cement mixture at a ratio (by weight)of one part BUSAN 11-M1® modified barium metaborate monohydrate, 45parts Type A portland cement, 140 parts washed masonry sand. Thismixture was inoculated with a spore/mycelial suspension of Aureobasidiumsp., covered with a specimen of vinyl pool liner, and incubated in ahumid environmental chamber at 32° C.±for 90 days. During the incubationperiod, the test substrate was moistened to maintain a wet interfacebetween the liner and the substrate.

The same substrate without BUSAN 11-M1® modified barium metaboratemonohydrate was prepared, inoculated, incubated, and moistened in anidentical manner as that with BUSAN 11-M1® modified barium metaboratemonohydrate.

Visual observations were made after 30, 60, and 90 days incubation. Thesurfaces of the substrates were examined using stereoscopic microscopetechniques. Substantial hyphal development and conidia germination wereobserved after 30 days on surfaces of the substrate that contained noBUSAN 11-M1® modified barium metaborate monohydrate. No hyphaldevelopment was observed on the substrate containing BUSAN 11-M1®modified barium metaborate monohydrate. Some hyphae were observed on theouter surfaces of the vinyl opposite to the surface in contact with thesubstrate containing BUSAN 11-M1® modified barium metaboratemonohydrate. Hyphae were observed on both the contact surface and outersurface of the vinyl in contact with the substrate containing no BUSAN11-M1® modified barium metaborate monohydrate.

Similar results were observed at examinations made after 60 and 90 daysincubation. Sporulation of the Aureobasidium sp. and a few airbornecontaminating fungi was observed after 60 days incubation on thespecimens that did not contain BUSAN 11-M1® modified barium metaboratemonohydrate.

After 90 days of incubation sporulation was observed on the following:

Substrate surface containing no BUSAN 11-M1® modified barium metaboratemonohydrate;

Vinyl surface in contact with substrates containing no BUSAN 11-M1®modified barium metaborate monohydrate;

Outer surface of vinyl in contact with substrate containing no BUSAN11-M1® modified barium metaborate monohydrate;

Outer surface of vinyl in contact with substrate containing BUSAN 11-M1®modified barium metaborate monohydrate.

After 90 days of incubation no sporulation was observed on thefollowing:

Substrate surface containing BUSAN 11-M1® modified barium metaboratemonohydrate; and

Vinyl surface in contact with substrate containing BUSAN 11-M1® modifiedbarium metaborate monohydrate.

From these observations, the following conclusions were made:

BUSAN 11-M1® modified barium metaborate monohydrate inhibits thedevelopment of hyphae and prevents sporulation of Aureobasidium sp. onthe surface of the substrate when dry blended into the substrate;

BUSAN 11-M1® modified barium metaborate monohydrate inhibits sporulationof Aureobasidium sp. on vinyl surfaces directly in contact with xsubstrates containing BUSAN 11-M1® modified barium metaboratemonohydrate; and

BUSAN 11-M1® modified barium metaborate monohydrate does not mitigate ordiffuse into vinyl liner when in direct contact with substratecontaining BUSAN 11-M1® modified barium metaborate monohydrate. This wasconcluded from evidence of growth by the fungus on the opposite surfaceof vinyl in contact with substrate containing BUSAN 11-M1® modifiedbarium metaborate monohydrate.

Replacement Pool Liner Procedures--Latex Spray

An alternative way to dry blending BUSAN 11-M1® modified bariummetaborate monohydrate into the base substrate was investigated. Theneed for this alternative was based on eliminating the requirement forreplacing existing base substrate in pools when liner replacements werebeing made. Based on the above successful results, it was assumed that atopical application of BUSAN 11-M1® modified barium metaboratemonohydrate to the surface of a base substrate already in place wouldinhibit the growth of stain causing fungi. This hypothesis was tested bythe following procedure.

A latex emulsion formulation containing BUSAN 11-M1® modified bariummetaborate monohydrate was developed that could be sprayed or brushapplied to the base substrate surfaces. The formulation was as follows:

    ______________________________________                                                                     Percent                                                                       of                                                                            Total                                            Material                     Weight                                           ______________________________________                                        Cellosize Hydroxyethyl Cellulose                                                                           76.8                                             (1% sol. QP-15,000 M Union Carbide HEC)                                       BUSAN 11-M1 ® modified barium metaborate monohydrate                                                   18.3                                             as received                                                                   Acrylic Latex - UV-433 (Union Carbide                                                                      4.8                                              UCAR Vehicle 443 total solids - 41% by weight)                                Busperse 39 - as received    0.1                                              (Buckman Labs - Sodium Polyacrylate)                                          ______________________________________                                    

This formulation is aqueous based, with a viscosity suitable forspray-application using conventional spray paint application equipmentor brush application.

Formulation/manufacturing equipment, as well as spray applicationequipment, can readily be cleaned by simply flushing and rinsing withwater. Product stability was confirmed by traditional procedures used totest stability of commercial latex emulsion paint and coating products.The formulation should be mixed in the container received prior toapplication.

A laboratory scale test of the efficacy of BUSAN 11-M1® modified bariummetaborate monohydrate in this formulation was made in conjunction withthe tests made in the dry-blend procedures, described above. Theformulation containing BUSAN 11-M1® modified barium metaboratemonohydrate was spray applied to the test sand/cement substrate at alevel equivalent to one gallon formulation per 100 square feet ofsubstrate surface. This provided a level of BUSAN 11-M1® modified bariummetaborate monohydrate of 1.8 pounds per 100 square feet of substratesurface. The formulation applied to the substrate was allowed topartially dry (i.e. stand for four hours) prior to inoculation andincubation. The same observations made with the dry-blend procedure weredone after 30, 60, and 90 days. Results and observations were comparedto a control preparation of the formulation containing no BUSAN 11-M1®modified barium metaborate monohydrate.

The observations confirmed that BUSAN 11-M1® modified barium metaboratemonohydrate applied in a water-based latex emulsion, at a level ofapproximately 1.8 pounds of BUSAN 11-M1® modified barium metaboratemonohydrate per 100 square feet of substrate surface, will inhibit thegrowth of Aureobasidium sp. under the conditions tested.

Other latex emulsion formulations containing BUSAN 11-M1® modifiedbarium metaborate monohydrate include:

    ______________________________________                                                                     Percent                                                                       of                                                                            Total                                            Material                     Weight                                           ______________________________________                                        Formulation 2                                                                 1% QR 708 sol. in water      76.8                                             (urethane thickener-Union Carbide)                                            BUSAN 11-M1 ® modified barium metaborate monohydrate                                                   18.3                                             Acrylic latex MV-23 (43% solids)                                                                           4.6                                              (Rohm and Haas)                                                               Busperse 39                  0.1                                              (Buckman Laboratories)                                                        Ethylene glycol monobutyl ether                                                                            0.2                                              (film former)                                                                 Formulation 3                                                                 2% RM 1020 sol in water      77.0                                             (Rohm & Haas)                                                                 BUSAN 11-M1 ® modified barium metaborate monohydrate                                                   18.3                                             Aquamac 430 (44.5% solids)   4.4                                              (McWhorter Acrylic emulsion)                                                  Tamol 850                    0.1                                              (Rohm & Haas)                                                                 Ethylene glycol monobutyl ether                                                                            0.2                                              Formulation 4                                                                 1.2% QP - 30000 HEC in water 77.0                                             (Union Carbide)                                                               BUSAN 11-M1 ® modified barium metaborate monohydrate                                                   18.3                                             Neocryl A-625                4.4                                              (45% sol. Zeneca Resins)                                                      BSI 75                       0.1                                              (Buckman Laboratories)                                                        Ethylene glycol monobutyl ether                                                                            0.2                                              Formulation 5                                                                 Natrosol 250 HR HEC          76.0                                             (1% in sol.) (Aqualon, Inc.)                                                  BUSAN 11-M1 ® modified barium metaborate monohydrate                                                   18.3                                             Acrylic Resin Neocryl A-640  4.0                                              (40% solids, Zeneca Resins)                                                   Orotan 930                   0.1                                              (Rohm & Haas)                                                                 Ethylene glycol monobutyl ether                                                                            0.2                                              Formulation 6                                                                 2% MPA 1075 in water         77.5                                             (Bentonite, Rheox)                                                            BUSAN 11-M1 ® modified barium metaborate monohydrate                                                   18.3                                             Synthemul 40-412             3.9                                              (50% solids, Reichhold                                                        Colloid 226/35 Dispersant    0.1                                              (Allied Colloids)                                                             Ethylene glycol monobutyl ether                                                                            0.2                                              ______________________________________                                    

SUPPLEMENTAL STUDIES

Vinyl Liner Compatibility

To confirm the compatibility of continuous contact of vinyl linersurfaces with substrates containing BUSAN 11-M1® modified bariummetaborate monohydrate, a series of observations have been made. Thephysical appearance of the liner samples used in the efficacy studieswere examined and compared to new liner samples. These samples were alsocompared to those in contact with substrate containing no BUSAN 11-M1®modified barium metaborate monohydrate. New vinyl liner samples werealso placed in direct contact with moistened BUSAN 11-M1® modifiedbarium metaborate monohydrate (as received) after a period of 150 days,no differences in the physical appearance of any of these vinyl samplescould be distinguished. There is no past history information that wouldindicate any incompatibility problems and BUSAN 11-M1® modified bariummetaborate monohydrate is used commercially as an additive in substratesfabricated with various vinyl resins.

BARIUM LEACHING STUDIES

The question of BUSAN 11-M1® modified barium metaborate monohydrate, asused in the proposed applications, contributing to hazardous levels ofsoluble Ba in ground waters was also addressed. Samples of thesubstrates used in the efficacy studies were analyzed by an independentlaboratory for soluble Ba in leachate. The tests were performed inaccordance with the Federal Register Vol. 45, No. 98, Part 261"Identification and Listing of Hazardous Waste," Subpart C, 261.24. Theresults indicated that barium levels in the leachates are less than 5.0mg/L.

This level is well below the level of "greater than 100 mg/L" which isthe lower limit that the EPA classifies as hazardous.

Other embodiments of the present invention will be apparent to thoseskilled in the art from consideration of the specification and practiceof the present invention disclosed herein. It is intended that thespecification and examples be considered as exemplary only, with a truescope and spirit of the present invention being indicated by thefollowing claims.

What is claimed:
 1. A dry blend mixture useful in controlling ormitigating staining of a liner in contact with the mixture caused inpart by at least an anaerobic, facultative anaerobic, or microaerophilicmicroorganism, said dry blend mixture comprising: a) sand and/orvermiculite, b) dry cement, and c) an amount of borate salt effective incontrolling or mitigating staining caused by the microorganism.
 2. Themixture of claim 1, wherein the borate salt is a sodium borate, ammoniumborate, lead borate, lithium borate, magnesium borate, potassium borate,strontium borate, zinc borate, or boric acid, or mixtures thereof. 3.The mixture of claim 1, wherein the borate salt is a metaborate salt, apyroborate salt, a tetraborate salt, or mixture thereof.
 4. The mixtureof claim 3, wherein the borate salt is a metaborate salt.
 5. The mixtureof claim 4, wherein the metaborate salt is calcium metaborate or bariummetaborate.
 6. The mixture of claim 1 wherein said mixture is present ata ratio of about one pound of said borate salt, per about 45 pounds ofsaid cement, and about 145 pounds of said sand or about 20 pounds ofsaid vermiculite per pound of borate salt.
 7. The mixture of claim 1wherein said mixture consist essentially of one pound of said boratesalt, per about 45 pounds of said cement, and about 145 pounds of saidsand or about 20 pounds of said vermiculite per pound of borate salt. 8.A method of applying a pool liner in an in-ground pool, comprisingapplying the dry blend mixture of claim 1 to the floor of an in-groundpool, and applying a pool liner to the dry blend mixture.